Chris, I've been having a very odd issue with URO for a few weeks and no-one I know can reproduce it. But I've now installed on Chrome rather than Chromium and still getting the problem, perhaps it's interference with another extension. But just in case you've seen it before or know what the issue is without me digging around here we go:

Sometimes (usually very often but not all the time), URO will try to fire up multiple copies of itself in the left hand box. At the moment I can only get it to do it in the beta but I'm sure I'm not imagining it happening in the production one too. In the console I get repeated:

It's error reports like this that make programmers weep with joy - the only thing that could have made it any better was if you'd fixed the code for me

The "white background" option requires access to one of the map layer elements in order to change the background colour, and it seems like on your system this layer isn't set up by the time URO acts on the option setting during script startup. I've tweaked the code so that it tests for the layer existence before trying to change the colour, and I'll upload a new version tonight.